Unidirectional respirator valve

ABSTRACT

A unidirectional valve, wherein the valve comprises a valve body including a frame, a valve opening through the frame, and a valve seat extending from the frame and at least partially surrounding the valve opening. The valve further includes a valve flap having a first portion attached to the frame and an adjacent second portion free to move from a first position where the second portion is in contact with at least a part of the valve seat to a second position where at least part of the second portion is spaced from the valve seat, wherein the valve flap has a nonuniform thickness. The thickness variations may occur between sides of the valve flap, and may also occur between the ends of the valve flap.

This application is a continuation of U.S. application Ser. No.09/888,732 filed Jun. 25, 2001, now allowed, the disclosure of which isherein incorporated by reference.

TECHNICAL FIELD

The present invention relates to respirator equipment for protecting thebreathing zone of users from gases, vapors, and particulates. Moreparticularly, the present invention provides a valve for use with suchrespirators.

BACKGROUND OF THE INVENTION

Various types of respirators are commonly worn by people who work inareas where the air may be contaminated with toxic or noxious substancessuch as airborne particulates, gases, and vapors. The type of respiratorused in a particular environment depends on the amount and type ofprotection required by the wearer.

One general category of respirators typically includes those having abreathing mask with at least one filtered air inlet and at least oneexhalation outlet or port. These respirators may be of the type referredto as half facepiece respirators, which typically cover the mouth andnose of the wearer, or of the type referred to as full facepiecerespirators, which additionally cover the face and eyes of the wearer.With these types of respirators, the wearer pulls air through thefiltered air inlet or inlets by drawing a breath, thereby creating anegative pressure in the mask. When the wearer exhales, the air releasedfrom the wearer's mouth creates a positive pressure in the mask, causingthe air to exit the mask through the exhalation outlet or port when thepositive air pressure reaches a certain level.

Another general type of respirator is referred to as a filteringfacemask, which generally includes a mask body made of a filteringmaterial that is permeable to air. The facemask may additionally includeat least one exhalation outlet or port. This type of respiratortypically covers the mouth and nose areas of the wearer. When in use,the wearer inhales and pulls air through the permeable mask material,then exhales and pushes air out of the facemask through the exhalationvalve or port.

The components used for a particular respirator should not makebreathing difficult for the wearer and ideally should allow the wearerto inhale and exhale comfortably when using the respirator. Respiratorcomponents that can affect the comfort of the respirator wearer are thevalves, which may include both exhalation and inhalation valves. Anexhalation valve selected for a respirator should allow a highpercentage of air to easily escape from the interior portion of thebreathing mask when the wearer exhales so that air pressure does notbuild up inside the mask. This can be accomplished by providing a valveportion that is displaced relatively easily from its valve seat when thewearer exhales. However, the valve portion also should seal easilyagainst the valve seat when the wearer is not exhaling so thatcontaminated or unfiltered air does not unintentionally leak into thewearer's breathing zone. Although an inhalation valve would similarlyallow for passage of air through the valve, it would typically bepositioned in the opposite orientation from an exhalation valve. In thisway, a valve portion would be displaced from its valve seat when thewearer inhales. It is also desirable that any valves provide the sameprotection to the wearer regardless of the orientation of therespirator.

SUMMARY OF THE INVENTION

In one aspect of this invention a unidirectional valve is provided,wherein the valve comprises a valve body including a frame, a valveopening through the frame, and a valve seat extending from the frame andat least partially surrounding the valve opening. The valve furtherincludes a valve flap having a first portion attached to the frame andan adjacent second portion free to move from a first position where thesecond portion is in contact with at least a part of the valve seat to asecond position where at least part of the second portion is spaced fromthe valve seat, wherein the valve flap has a nonuniform thickness. Thethickness variations may occur between sides of the valve flap, and mayalso occur between the ends of the valve flap.

In another aspect of this invention, a respirator is provided having aunidirectional valve, the respirator comprising a face mask having atleast one opening for receiving a unidirectional valve, wherein theunidirectional valve comprises a valve body including a frame, a valveopening through the frame, and a valve seat extending from the frame andat least partially surrounding the valve opening. The valve flap has afirst portion attached to the frame and an adjacent second portion freeto move from a first position where the second portion is in contactwith at least a part of the valve seat to a second position where atleast part of the second portion is spaced from the valve seat, whereinthe valve flap has a nonuniform thickness.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will be further explained with reference to theappended Figures, wherein like structure is referred to by like numeralsthroughout the several views, and wherein:

FIG. 1 is a perspective view of a respirator in accordance with thepresent invention;

FIG. 2 is a perspective view of a respirator similar to that of FIG. 1,with certain components omitted;

FIG. 3 is a side view of a valve diaphragm in accordance with thepresent invention;

FIG. 4 is a side view of the valve assembly of FIG. 1;

FIG. 5 is a perspective view of another aspect of a valve diaphragm;

FIGS. 6 a and 6 b are front views of valve diaphragms in accordance withthe present invention;

FIG. 7 is a side view of another valve assembly of the invention;

FIG. 8 is a side view of another valve assembly of the invention; and

FIG. 9 is a perspective view of another respirator arrangement inaccordance with the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the Figures, wherein the components are labeled withlike numerals throughout the several Figures, and initially to FIGS. 1and 2, one embodiment of an air purifying respirator 10 is illustrated,which is generally of the type referred to as a half facepiecerespirator. Respirator 10 includes a flexible face piece 12 having twoopenings or ports 14 to which air inlet assemblies 16 are fitted orsecured, and an opening 18 to which an exhalation valve assembly 20 isfitted or secured. As shown, air inlet assemblies 16 are positioned onopposite sides or ends of face piece 12 and are positioned low on theface piece so as to not obstruct the view of a person wearing therespirator. Opening 18 is located in the central area of the face piece12 so that it is generally in front of the mouth or breathing zone ofthe wearer. Each of the openings 14, 18 extend into the interior area offace piece 12.

Air inlet assemblies 16 can comprise chemical cartridges, air lines,particulate filters, or other various components. Assemblies 16 may alsoinclude a combination of several components to achieve specificqualities of the air entering a wearer's breathing space. In one aspectof the invention, openings 14 are generally cylindrical in shape andeach has a circular flange 22 that extends outwardly from face piece 12.Each of these flanges 22 is designed to receive a mating fitting (notshown) of one of the air inlet assemblies 16 to allow for secureattachment of the assemblies 16 to the face piece 12. For the aspectshown, flange 22 has three tabs 26 that are designed to engage with achannel (not visible) on the mating fitting. The inside diameter of themating fitting is slightly larger than the outer diameter of flange 22so that the pieces can fit securely together without interfering witheach other during attachment of assemblies 16. To secure an assembly 16to a flange 22, the mating fitting is slid over flange 22 until the tabs26 engage with a channel on the inside that fitting. The assembly 16 isthen rotated until the tabs 26 lock into place in the channel. Thisdesign allows for relatively easy detachment of assemblies 16 fromflanges 22 when desired. However, it is understood that any of a numberof alternate configurations may be used to secure the assemblies 16 tothe face piece 12, where the assemblies 16 may be removable andreplaceable, or may be permanently secured. While the above describedmethod of attachment does not require additional tools for attaching andremoving the air inlet assemblies, other attachment methods may requiretools.

Face piece 12 comprises a nose portion 40 that extends from the upperportion of a body portion 42. Body portion 42 is shaped to conformgenerally to the shape of a wearer's face, and is at least partiallyconvex in shape. The body and nose portions 40, 42 should be largeenough so that the face piece material is positioned at a comfortabledistance from the wearer's face when in use, but should be small enoughto provide a secure fit between the face piece 12 and the wearer's face.The size and shape of the nose and body portions 40, 42 may vary widely,depending on the particular aesthetic and functional requirements of therespirator.

Face piece 12 may be made of any of a variety of materials, includingflexible materials such as silicone, rubber, or thermoplasticelastomers, such as those commercially available under the tradedesignations “Kraton” from Shell Oil of Houston, Tex., “Monprene” fromTeknor Apex of Pawtucket, Rhode Island, and “Santoprene” from AdvancedElastomer Systems of Akron, Ohio. However, a wide range of materialswith various flexibilities would be appropriate for face piece 12.

As discussed above, exhalation valve assembly 20 is fitted in opening 18of face piece 12, as is illustrated in FIGS. 1 and 2, where FIG. 2 showsthe valve assembly 20 without some of its components to better view thevarious features of the assembly. Exhalation valve assembly 20 generallyincludes a frame 50 having an opening or orifice 52, a valve seat 54extending generally around the periphery of opening 52, and a valvediaphragm 56. Opening 52 can further include support members 53 that canprovide reinforcement and stabilize the frame 50. The support members 53can further prevent valve diaphragm 56 from being pulled through opening52 and into the interior area of face piece 12 during air pressurechanges.

Opening 52 is shown as a partially flattened oval in shape, however, anynumber of shapes would be possible. Valve seat 54 may closely match thesize and shape of the periphery of opening 52, or may have a differentsize and/or shape than opening 52. In one aspect of the invention, theopening 52 has the same general outer periphery size and shape as thesize and shape of the periphery of the inside of valve seat 54. In anycase, valve seat 54 has a top surface 58 which can be generally smoothor may be textured, where the smoothness of top surface 58 can affectthe level of sealing achieved between valve diaphragm 56 and top surface58. Frame 50 further includes two attachment holes 60, which will befurther discussed below. As shown, attachment holes 60 are located abovethe valve seat 54, thereby providing an attachment point for valvediaphragm 56 that is outside the opening 52.

Additionally referring to FIGS. 3 and 4, one embodiment of valvediaphragm 56 is shown, where diaphragm 56 includes a flap portion 70having a top surface 72, a bottom surface 74, a first end 76, and asecond end 77. In this embodiment, flap portion 70 has a constantcurvature that extends from first end 76 to second end 77 and the topsurface 58 of valve seat 54 defines an essentially flat plane. When thediaphragm 56 is installed on frame 50, the curvature of flap portion 70toward valve seat 54 creates a bias in flap portion 70 such that thecurve of at least a portion of flap portion 70 may flatten or straightento some degree as it comes in contact with top surface 58 of valve seat54. In one aspect of the invention, the bias created by the curvature offlap portion 70 is substantial enough to keep flap portion 70 sealedagainst top surface 58 in all orientations.

Alternatively, flap portion 70 may have a side profile that does notinclude a constant curvature. For example, the curvature of flap portion70 may vary from first end 76 to second end 77. Many other variations ofthe side profile of flap portion 70 are also considered to be with thescope of this invention, where the creation of a bias of the flapportion 70 toward valve seat 54 helps to keep flap portion 70 in asealed position when it is not subjected to external forces such as airpressure changes.

Flap portion 70 may vary in thickness from first end 76 to second end77. For one example, flap portion 70 has a thickness T1 at first end 76that is greater than its thickness T2 at second end 77. The thickness offlap portion 70 may taper gradually from first end 76 to second end 77,as shown, or the thickness can vary less gradually, such as in a type of“step” arrangement. Thickness T1 may alternatively be smaller thanthickness T2. Variations in the thickness of flap portion 70 from oneend 76 to the other end 77 may be chosen to achieve certain performancecharacteristics of the valve diaphragm 56, such as a desired amount offorce needed to move the flap portion from its closed position to itsopen position. For example, the flap portion thickness may be smaller inareas where it would be desirable to decrease the force necessary tomove the flap portion 70 from one position to another. A wide range ofthickness variations are contemplated by the present invention, however,in one aspect of the invention, a difference in the thickness at anypoint between first end 76 and second end 77 of greater than about 10%is desirable.

Two connectors 80 extend from the bottom surface 74 of flap portion 70,which are used for attachment of diaphragm 56 to frame 50. Connectors 80include a protrusion 82 and a tapered cap 84, where the cap 84 tapersfrom a first end 86 having a diameter D1 (which is essentially a pointin this example) up to a second end 88 that has a diameter D2 that isgreater than the diameter D1 of first end 86. In this aspect ofdiaphragm 56, both the flap portion 70 and connectors 80 are made of arelatively flexible material. Connectors 80 are designed to be receivedby attachment holes 60, where the diameter D2 of second end 88 of cap 84is larger than the diameter of the attachment hole 60 in which it is tobe received. In order to engage each connector 80 with its respectiveattachment hole 60, cap 84 is pressed or pulled into the hole 60 untilthe outside diameter of cap 84 matches the inside diameter of the hole60. Additional force is then applied to the connector to temporarilycompress and deform cap 84 until second end 88 passes through hole 60.At this point, the connector 80 is positioned so that the flap portion70 is on one side of frame 50, the protrusion 82 is positioned withinthe hole 60, and the tapered cap 84 is on the opposite side of frame 50,thereby securing diaphragm 56 to frame 50. To remove a diaphragm 56 froma frame 50, each connector 80 would be pushed or pulled in the oppositedirection through its respective hole 60.

The above discussion of the use of connectors to attach a diaphragm 56to frame 50 is only one of many types of attachment methods contemplatedby the present invention. The attachment method chosen for a particularapplication may provide for either temporary or permanent attachment ofdiaphragm 56 to frame 50, although a temporary attachment method canallow for removal and replacement of diaphragms as desired. Thediaphragm 56 may be secured to frame 50 by any of a number of knownattachment methods, including the use of connectors extending from asurface of flap portion 70 that have a different configuration than theconnectors 80 described above. It is also understood that more or lessthan two connectors 80 may be used for a particular valve diaphragm.Alternatively, the diaphragm 56 may be attached to frame 50 through theuse of repositionable or permanent adhesives, hook and loop typefasteners, screws or other mechanical fasteners, welding, or othersuitable attachment methods. In any of these attachment methods, theflap portion 70 and the attachment devices or materials may be made ofthe same or different materials. For one example, the flap portion maybe made of a thermoset elastomer and attached to a frame by a metalscrew or rivet. For another example, the entire valve diaphragm 56,including the flap portion and attachment means, may be made of a singlematerial.

In another aspect of the invention, diaphragm 56 is integrally molded tothe frame 50 so that it is not detachable and replaceable from frame 50.In this embodiment, the frame 50 and diaphragm 56 could be removable andreplaceable as an integral unit from the face piece 12, if desired.

Referring now to FIG. 5, one aspect of diaphragm 56 includes multipleribs 90 extending from the top surface 72 of flap portion 70 for atleast part of the distance from the first end 76 to second end 77. Inthis embodiment, the base part of flap portion 70 has a uniformthickness. The ribs 90 provide additional stiffness to the diaphragm 56,which can be useful in providing the desired seal between the flapportion 70 and the valve seat 54 while minimizing the mass added to theflap portion 70. Further, a flap portion with ribs can have less massthan flap portions that are relatively thick across their entireprofile, while achieving the same level of stiffness. In other words,the ratio of stiffness of the flap portion to the mass of the flapportion can be greater by adding ribs than by increasing the thicknessacross the entire flap portion. When the stiffness to mass ratio of aflap portion 70 is higher, the preload force or amount of bias requiredto keep valve diaphragm 56 sealed against valve seat 54 would be lower.In addition, the force required to open a particular valve diaphragmhaving a high stiffness to mass ratio can be lower than the forcerequired to open a valve diaphragm having a low stiffness to mass ratio.

The length, width, and thickness of each rib 90 can be chosen to achievethe desired level of stiffness for the flap portion 70. A single rib 90or multiple ribs 90 may be used, where the design of each rib 90 may bethe same or different than other ribs 90 on the same flap portion 70.Each rib 90 may also vary from one end of the rib to the other end ofthe rib. For example, each rib 90 may be wider or thicker at one end ofthat rib than at the other end of that rib. The rib or ribs may alsoextend for only part of the distance between the first end 76 of flapportion 70 to second end 77. In any case, the number, size, and shape ofribs used should provide a desired level of stiffness to the valvediaphragm while allowing enough flexibility so that the valve diaphragmcan open under normal pressure changes.

As discussed above, flap portion 70 may vary in thickness from one endto the other. Flap portion 70, which further includes a first side 78and a second side 79 in at least one aspect of the invention, may alsovary in thickness from side 78 to side 79. For one example, flap portion70 can have a thickness at first side 78 that is different than thethickness at second side 79. The thickness of flap portion 70 may tapergradually from first side 78 to second side 79 or the thickness can varyless gradually, such as in a type of “step” arrangement, or in any otherregular or irregular variation from one side to the other. Further, theinclusion of at least one rib on a particular flap portion may also beconsidered to be a thickness variation across that flap portion.

FIG. 6 a shows an end view of a flap portion 70 a, where the flapportion is thickest near first side 78 a and second 79 a and thinnestnear the middle of the flap portion 70 a. Another example of varying thethickness of a flap portion is illustrated in FIG. 6 b. As shown, thetop surface 72 b of the flap portion 70 b varies in a sinusoidal patternfrom the first side 78 b to second side 79 b, thereby providing portionsof flap portion 70 b with different thicknesses. It is understood thatany number of thickness variations, both regular and irregular, acrossthe surface of a particular flap portion are possible and are consideredto be within the scope of the present invention. In one aspect of theinvention, however, a difference in the thickness at any point betweenthe first side 78 and the second side 79 of greater than about 10% isdesirable. Like the addition of ribs to a flap portion, these thicknessvariations can also provide an increased stiffness to mass ratio for aflap portion as compared to a flap portion with uniform thickness fromside to side.

One aspect of valve diaphragm 56 includes a flap portion 70 made of athin membrane or film of relatively flexible material such as silicone,rubber, or a thermoplastic elastomer, for example. A wide variety offlexible materials may be suitable for flap portion 70, where thematerial is selected to provide the desired level of stiffness to keepthe diaphragm 56 sealed against the valve seat 54 when diaphragm 56 isin its closed position, yet provide the desired level of flexibility toallow diaphragm 56 to move away from the valve seat 54 to an open orsemi-open position. When valve diaphragm 56 includes additional elementson the top surface 72 of flap portion 70 (such as ribs 90, for example),the additional elements may be the same material as or a differentmaterial from the flap portion 70. For example, the additional elementsmay be made of a material such as a thermoplastic elastomer, plastic,metal, or composite. Again, the material for these components would beselected to provide the desired level of stiffness for a particulardiaphragm 56.

Flap portion 70 may further have a shape or “footprint” such as thatshown in FIG. 5, where first end 76 is generally parallel to second end77 and first side 78 is generally parallel to second side 79, howevermany other shapes for flap portion 70 are possible. The selection of theflap portion shape will depend on the shape and arrangement of the othervalve and respirator components and also on the performancecharacteristics desired for each particular valve assembly.

The flap portion 70 may be manufactured using any method that providesthe desired shape, size and curvature of the flap portion. For oneexample, the flap portion 70 can be molded using standard moldingtechniques, such as compression molding or injection molding. Foranother example, flap portion 70 can be extruded to form a particularprofile from either the side or the end of the flap portion 70, which issometimes referred to as profile extrusion.

In operation, valve diaphragm 56 rests or seals against valve seat 54when in its closed position, where a better seal is typically achievedwhen more of the surface area of the valve seat 54 comes in contact witha corresponding portion of the valve diaphragm 56. An illustration ofvalve diaphragm 56 with its flap portion 70 in a closed position isshown in FIG. 4 in solid lines. When flap portion 70 has a curvature asdescribed above, this curve would be at least partially flattened outonto a valve seat 54 that is generally planar, as illustrated. In thisway, the valve diaphragm 56 is preloaded with the curvature of the flapportion 70, which provides the necessary sealing force to keep the valvediaphragm 56 in its closed position when not subjected to other forces.When the wearer exhales air, the air pressure inside respirator 10increases until the pressure becomes sufficiently high that the valvediaphragm 56 is forced away from the valve seat 54 in the directionshown by arrow A. With a certain amount of pressure that depends on theparticular respirator components used, the flap portion will bedisplaced into the position shown by broken lines and indicated byreference number 70′.

In one aspect of the invention, connectors 80 are located closer to thefirst end 76 of flap portion 70 than the second end 77. When the valveassembly 20 is assembled, the valve diaphragm 56 is thus supported in acantilever style arrangement, where the area of the diaphragm 56 closestto first end 76 is secured to the frame 50 so that its movement islimited relative to frame 50, while the area of the diaphragm 56 closestto second end 77 has more freedom to move relative to frame 50. Thisarrangement allows the valve diaphragm to move from an open position toa closed position, depending on the breathing action of the wearer. Whenthe diaphragm 56 is secured to frame 50 at its furthest point from thefree end 77 of the flap portion 70, the longest possible moment arm iscreated. The moment arm for this aspect of the invention is defined asthe distance from the attachment point of the flap portion 70 to thefree end of the flap portion that is furthest from the attachment point.In this way, for a given pressure, the opening distance of the secondend 77 of flap portion 70 from valve seat 54 is greater than if themoment arm were shorter.

In another aspect of the invention, the flap portion 70 would have anintermediate connector or connectors that would secure to the frame 50so that two or more cantilever style flaps are created on either side ofthe connector or connectors. In this type of arrangement, the opening inthe face piece may have an intermediate supporting structure to whichthe connector or connectors can attach, or there may actually be two ormore openings or orifices in the front part of the face piece. Each ofthe multiple cantilever style flaps would preferably be positioned overan opening or orifice for sealing thereof.

In another aspect of the present invention shown in FIG. 7, a valvediaphragm 156 is provided with a flap portion 170 that is a flat orplanar piece. In this aspect, the diaphragm 156 is attached at an anglerelative to the generally flat plane of valve seat 154, thereby bendingthe flap portion 170 relative to the valve seat 154 and providing thenecessary preload or bias to keep the valve diaphragm in its closedposition when the respirator is not subject to pressure changes. Thediaphragm 156 may have any of the thickness or profile variationsdiscussed above relative to valve diaphragm 56.

Alternatively, valve diaphragm 256 may be provided with a flap portion270 that is a flat or contoured piece and the valve seat 254 is notplanar, as shown in FIG. 8. In this aspect of the present invention, thecurvature of valve seat 254 creates the necessary preload to keep thevalve diaphragm 254 in its closed position when desired. Again, valvediaphragm 256 may have any of the thickness or profile variationspreviously discussed relative to valve diaphragm 56. While the abovedescription is directed to a half facepiece type respirator, the valveof the present invention is not intended to be limited to this type ofrespirator. In another aspect of the present invention, FIG. 9illustrates a filtering face mask respirator 310, which generallyincludes a mask body 312 made of a filtering material that is permeableto air and an exhalation valve assembly 320. With this type ofrespirator, air can be pulled into the wearer's breathing zone throughthe mask material of mask body 312 when the wearer inhales. The maskmaterial should provide sufficient filtering capability to filterundesirable contaminants (such as gases and particulates) from the airentering the wearer's breathing zone when the wearer inhales. Mask body312 has an opening 318 in the general area of a respirator wearer'smouth over which at least a portion of exhalation valve assembly 320 ispositioned. Exhalation valve assembly 320 generally includes a frame 350having an opening or orifice, a valve seat, and a valve diaphragm 352.The several components that make up the exhalation valve assembly 320may include any of the variations and features discussed above relativeto valve assembly 20. Thus, the exhalation valve assembly 320 would alsooperate in essentially the same manner as that described above relativeto the operation of valve assembly 20.

In addition to the types of respirators described above, the valve ofthe present invention is intended to be useful for other types ofrespirator arrangements where it is desirable to provide a valve thatcan move from its sealed position to an open position through thebreathing action of the respirator wearer, such as full facepiecerespirators, powered air-purifying respirators, valved hood respirators,welding shields and other respirator arrangements. These arrangementsmay include one or more valves of the type contemplated by the presentinvention.

It is further contemplated that the valve of the present invention beused as an inhalation valve. In this arrangement, the inhalation valveassembly operates in essentially the same way as the exhalation valve,where the valve diaphragm is similarly sealed and displaced from thevalve seat depending on the difference in pressure generated inside therespirator by the wearer's breathing action. In the case of aninhalation valve, however, the valve diaphragm would be facing theinterior of the respirator so that it can open toward the wearer's face.Thus, inhalation by the wearer creates the necessary negative pressureinside the respirator to pull the diaphragm away from the valve seatinto its open position. When the user exhales, the pressure increasesinside the respirator, thereby allowing the diaphragm to move backtoward its sealed position.

The present invention has now been described with reference to severalembodiments thereof. The entire disclosure of any patent or patentapplication identified herein is hereby incorporated by reference. Theforegoing detailed description and examples have been given for clarityof understanding only. No unnecessary limitations are to be understoodtherefrom. It will be apparent to those skilled in the art that manychanges can be made in the embodiments described without departing fromthe scope of the invention. Thus, the scope of the present inventionshould not be limited to the structures described herein, but only bythe structures described by the language of the claims and theequivalents of those structures.

1. A respirator comprising: a face mask comprising an opening formedtherethrough; and a unidirectional valve comprising a valve flap locatedover the opening of the face mask, wherein the valve is movable from afirst position in which the opening is closed by the valve flap to asecond position in which a portion of the valve flap is spaced from theopening such that fluids can pass through the opening, wherein the valveflap comprises a nonuniform thickness.
 2. A respirator according toclaim 1, wherein the valve flap comprises a first end and a second endopposite the first end, wherein the first end is attached to the facemask and wherein the second end is not attached to the face mask.
 3. Arespirator according to claim 1, wherein the valve flap comprises afirst end and a second end opposite the first end, wherein the first endis attached to the face mask and wherein the second end is not attachedto the face mask, and further wherein the valve flap is thicker at thefirst end than at the second end.
 4. A respirator according to claim 1,wherein the valve flap comprises a first end and a second end oppositethe first end, wherein the first end is attached to the face mask andwherein the second end is not attached to the face mask, and wherein thevalve flap is thicker at the first end than at the second end, andfurther wherein the nonuniform thickness of the valve flap tapersgradually from the first end to the second end.
 5. A respiratoraccording to claim 1, wherein the valve flap comprises a first end and asecond end opposite the first end, wherein the first end is attached tothe face mask and wherein the second end is not attached to the facemask, and wherein the valve flap is thicker at the first end than at thesecond end, and further wherein the nonuniform thickness of the valveflap tapers gradually from the first end to the second end.
 6. Arespirator according to claim 1, wherein the valve flap comprises afirst end and a second end opposite the first end, wherein the first endis attached to the face mask and wherein the second end is not attachedto the face mask, and further wherein the valve flap is thicker at thesecond end than at the first end.
 7. A respirator according to claim 1,wherein the valve flap comprises a first end and a second end oppositethe first end, wherein the first end is attached to the face mask andwherein the second end is not attached to the face mask, and wherein thevalve flap is thicker at the second end than at the first end, andfurther wherein the nonuniform thickness of the valve flap tapersgradually from the second end to the first end.
 8. A respiratoraccording to claim 1, wherein the face mask comprises a half facepiecerespirator.
 9. A respirator according to claim 1, wherein the face maskcomprises a mask body made of filtering material that is permeable toair, and wherein the opening is formed in the mask body.
 10. Arespirator according to claim 1, wherein the valve flap comprises acurvature, and wherein the curvature of the valve flap is at leastpartially flattened when the valve flap is in the first position inwhich the opening is closed by the valve flap.
 11. A respiratorcomprising: a face mask comprising a mask body made of filteringmaterial that is permeable to air; an opening formed through the maskbody; and a unidirectional valve comprising a valve flap located overthe opening formed through the mask body, wherein the valve is movablefrom a first position in which the opening is closed by the valve flapto a second position in which a portion of the valve flap is spaced fromthe opening such that fluids can pass through the opening, wherein thevalve flap comprises a nonuniform thickness, and wherein the valve flapcomprises a first end and a second end opposite the first end, whereinthe first end is attached to the face mask and wherein the second end isnot attached to the face mask.
 12. A respirator according to claim 11,wherein the valve flap comprises a first end and a second end oppositethe first end, wherein the first end is attached to the face mask andwherein the second end is not attached to the face mask, and furtherwherein the valve flap is thicker at the first end than at the secondend.
 13. A respirator according to claim 11, wherein the valve flapcomprises a first end and a second end opposite the first end, whereinthe first end is attached to the face mask and wherein the second end isnot attached to the face mask, and wherein the valve flap is thicker atthe first end than at the second end, and further wherein the nonuniformthickness of the valve flap tapers gradually from the first end to thesecond end.
 14. A respirator according to claim 11, wherein the valveflap comprises a first end and a second end opposite the first end,wherein the first end is attached to the face mask and wherein thesecond end is not attached to the face mask, and wherein the valve flapis thicker at the first end than at the second end, and further whereinthe nonuniform thickness of the valve flap tapers gradually from thefirst end to the second end.
 15. A respirator according to claim 11,wherein the valve flap comprises a first end and a second end oppositethe first end, wherein the first end is attached to the face mask andwherein the second end is not attached to the face mask, and furtherwherein the valve flap is thicker at the second end than at the firstend.
 16. A respirator according to claim 11, wherein the valve flapcomprises a first end and a second end opposite the first end, whereinthe first end is attached to the face mask and wherein the second end isnot attached to the face mask, and wherein the valve flap is thicker atthe second end than at the first end, and further wherein the nonuniformthickness of the valve flap tapers gradually from the second end to thefirst end.
 17. A respirator according to claim 11, wherein the valveflap comprises a curvature, and wherein the curvature of the valve flapis at least partially flattened when the valve flap is in the firstposition in which the opening is closed by the valve flap.
 18. Arespirator comprising: a face mask comprising a mask body made offiltering material that is permeable to air; an opening formed throughthe mask body; and a unidirectional valve comprising a valve flaplocated over the opening formed through the mask body, wherein the valveis movable from a first position in which the opening is closed by thevalve flap to a second position in which a portion of the valve flap isspaced from the opening such that fluids can pass through the opening,wherein the valve flap comprises a first end and a second end oppositethe first end, wherein the first end is attached to the face mask andwherein the second end is not attached to the face mask, and furtherwherein the valve flap is thicker at the first end than at the secondend.
 19. A respirator according to claim 18, wherein the thickness ofthe valve flap tapers gradually from the first end to the second end.20. A respirator according to claim 18, wherein the valve flap comprisesa curvature, and wherein the curvature of the valve flap is at leastpartially flattened when the valve flap is in the first position inwhich the opening is closed by the valve flap.